Mike Borgelt wrote:
The NS article pointed at ways, through the use of cascading fractals, that we could overcome the limitations of even the very short term weather predictions available at present. RASP is currently running on a 12km grid - and soaking up all the computational resources that our sponsor can provide. One of the issues that this produces is that the geography in he model is also "smeared". For the Darling Downs, this means that Toowoomba range is not a steep escarpment but a relatively gentle slope. The effect of this in the model is to significantly over-emphasise the maritime incursion should there be any on the coast. It also makes it very hard (effectively impossible) to model the Bunya wave system. These situations arise not as some longterm future date of a weather prediction, but within 24 hours of the forecast date. The direction discussed in the article offers hope that there will be ways to significantly improve the accuracy of short term weather forecasts without significantly improving the computational intensity. Note also that little "s" in "models". Recently a physicist pointed out the problem with that little "s", that's right it is "models" not "model". If there is nothing but physics there would be only one "model". That there are many (last count 23 major ones even the BoM uses 3 different ones) is a result of the "parameterisations" mentioned in the NS article. Every group has their favourite numbers. Who is right? They all are - sometimes. They are all wrong sometimes. This is considered to be better than reading tea leaves or chicken entrails.There is nothing surprising in there being multiple, different models of the atmosphere. First of all, as soon as you build any mathematical simulation of a physical world system, even very simple ones, it is an abstraction - a model. Science allows us to build very many very successful models - including really complex ones. With a system as complex as a planetary atmosphere, it is also unsurprising that there are multiple models as many different teams will build models for a whole variety of reasons (a major one being the "Not Invented Here" syndrome). The point in the article was that all the major models appeared to demonstrate the fractal cascade effect. Oh - and all the various major models provide significantly better short term results than reading tea leaves or chicken entrails! -- Robert Hart [email protected] +61 (0)438 385 533 http://www.hart.wattle.id.au |
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